[libvirt] PATCH: recent qemu-kvm requires -enable-kvm flag to activate VT optimization

[Daniel Veillard]

On Sun, Nov 15, 2009 at 07:03:51PM -0800, Steve Yarmie wrote:
> Hello,
>
> Recent qemu releases require command option '-enable-qemu' in order
> for the kvm functionality be activated. Libvirt needs to pass this flag 
> to qemu when starting a domain. Note that without the option,
> even if both the kernel and qemu support KVM, KVM will not be activated
> and VMs will be slow as molasses ;)
>
> I added a check in qemu_conf.c to see if `qemu -help` emits the -enable-kvm
> flag, and if so, use the flag accordingly.
>
> There exists a check in src/qemu/qemu_conf.c to check for the -no-kvm flag.
> This check works the same way. 
>
> Adding the included code will not break systems where qemu does not
> have the option.
>
> See 'qemu -help':
> ...
> -enable-kvm     enable KVM full virtualization support ...
>
> included patch against src/qemu/qemu_conf.{c,h}  
>
> -Steve
>
>

> diff -ur libvirt/src/qemu/qemu_conf.c libvirt-qemu-enable-kvm/src/qemu/qemu_conf.c
> --- libvirt/src/qemu/qemu_conf.c	2009-11-08 20:57:08.438908134 -0800
> +++ libvirt-qemu-enable-kvm/src/qemu/qemu_conf.c	2009-11-08 22:36:04.299921427 -0800
> @@ -1602,6 +1602,7 @@
>      struct utsname ut;
>      int disableKQEMU = 0;
>      int disableKVM = 0;
> +    int enableKVM = 0;
>      int qargc = 0, qarga = 0;
>      const char **qargv = NULL;
>      int qenvc = 0, qenva = 0;
> @@ -1660,6 +1661,15 @@
>          def->virtType == VIR_DOMAIN_VIRT_QEMU)
>          disableKVM = 1;
>  
> +    /* Should explicitly enable KVM if
> +     * 1. Guest domain is 'qemu'
> +     * 2. The qemu binary has the -enable-kvm flag
> +     * NOTE: user must be responsible to load the kvm modules
> +     */
> +    if ((qemuCmdFlags & QEMUD_CMD_FLAG_ENABLE_KVM) &&
> +        def->virtType == VIR_DOMAIN_VIRT_QEMU)
> +        enableKVM = 1;
> +
>      /*
>       * Need to force a 32-bit guest CPU type if
>       *
> @@ -1787,6 +1797,8 @@
>          ADD_ARG_LIT("-no-kqemu");
>      if (disableKVM)
>          ADD_ARG_LIT("-no-kvm");
> +    if (enableKVM)
> +	ADD_ARG_LIT("-enable-kvm");
>      ADD_ARG_LIT("-m");
>      ADD_ARG_LIT(memory);
>      if (def->hugepage_backed) {
> diff -ur libvirt/src/qemu/qemu_conf.h libvirt-qemu-enable-kvm/src/qemu/qemu_conf.h
> --- libvirt/src/qemu/qemu_conf.h	2009-11-08 20:57:08.438908134 -0800
> +++ libvirt-qemu-enable-kvm/src/qemu/qemu_conf.h	2009-11-08 14:57:39.000000000 -0800
> @@ -73,6 +73,7 @@
>      QEMUD_CMD_FLAG_XEN_DOMID     = (1 << 20), /* -xen-domid (new style xen integration) */
>      QEMUD_CMD_FLAG_MIGRATE_QEMU_UNIX = (1 << 21), /* Does qemu support unix domain sockets for migration? */
>      QEMUD_CMD_FLAG_CHARDEV       = (1 << 22), /* Is the new -chardev arg available */
> +    QEMUD_CMD_FLAG_ENABLE_KVM    = (1 << 23), /* Is the -enable-kvm flag available to "enable KVM full virtualization support" */
>  };
>  
>  /* Main driver state */

 Patch seems incomplete as I don't see any detection code setting up
QEMUD_CMD_FLAG_ENABLE_KVM in qemuCmdFlags

Daniel

-- 
Daniel Veillard      | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
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